BanG Dream/Prototype

Yeah, this really feels like a first draft. Nebulous characterizations, plot contrivances, awkward progression...

There's also a light novel version. I have yet to read it though to know if there are any differences between the two.

What exactly is this? Without the context of the anime, I can see that it's telling basically the same story as this, but the characters are radically different.

This is the original story with the original character personalities back in 2015. Later on they got a reset/reboot to become the characters we know now. Since this is a multimedia franchise that incorporates the seiyuus, they made the new character personalities reflect the seiyuus personalities better.

Interesting. Looking on Wikipedia, it says this series is still running?

The BanG Dream! franchise as a whole is still running and running very well. This manga however only has 12 chapters and is completed.

What exactly is this? Without the context of the anime, I can see that it's telling basically the same story as this, but the characters are radically different.

This is the original story with the original character personalities back in 2015. Later on they got a reset/reboot to become the characters we know now. Since this is a multimedia franchise that incorporates the seiyuus, they made the new character personalities reflect the seiyuus personalities better.

Ok, from WHERE does this comes from?

Believe it or not, this is an official work and not a doujin for BanG Dream!/Bandori. Originally published by in Corocoro Aniki.
https://twitter.com/bang_dream_info/status/875270873015435265
https://twitter.com/bandori_updates/status/875273620980776960/photo/1